Hmm, I've always used cos for x and sin for y, because it's correct according to my math teacher and the sin/cos circle thingy (the Unit Circle? I forget its name.)
Me too. The problem is that on a computer the second axis (y) is inverted compared to traditional trigonometry. Thus the y coordinate for computers would be -cos(angle).That's why most people just reverse x and y orientation, otherwise you get a lot of "interesting" results when trying to use it with ATan2 and RotateImage (which uses angles like in navigation, not trigonometry).
That way, 0 faces to the right like it should, and increasing angles go clockwise.
Except increasing angles are supposed to go counter-clockwise!